The invention relates to a low-pressure mercury vapor discharge lamp comprising a tubular discharge vessel, which is arranged within a lamp envelope and curved at a number of areas. The vessel is sealed in a gastight manner and filled with mercury and a rare gas. Electrodes are arranged at the ends of the discharge vessel and are located at the same end of the space within the lamp envelope. A fluorescent lamp of this type is known from U.S. Pat. No. 4,383,200.
The known lamp comprises a discharge tube located within the lamp envelope and bent into the form of a hook. The lamp has small dimensions and serves as an alternative to an incandescent lamp for general illumination purposes.
The discharge vessel of this lamp is surrounded by the lamp envelope. During operation of the lamp the temperature easily increases to such a high value that the optimum mercury vapor-pressure for the conversion of supplied energy into ultraviolet resonance radiation of mercury in the discharge vessel (approximately 6.times.10.sup.-3 Torr) is exceeded. It is then necessary to take special measures in order to stabilize the mercury vapor-pressure at the optimum value, for example by providing a vapor-pressure controlling amalgam in the discharge vessel or by providing the discharge vessel with an appendix which is kept at a relatively low temperature (see U.S. Pat. No. 4,546,284). It is, however, complicated to provide such an appendix.
Moreover, the discharge vessel of the known lamp is secured only on one side within the lamp envelope. This makes the lamp vulnerable to vibrations and shocks.